Experimental Modal Analysis of Distinguishing Microstructural Variations in Carbon Steel SA516 by Applied Heat Treatments, Natural Frequencies, and Damping Coefficients

2021 ◽  
Author(s):  
Mohammadreza Ahmadpar ◽  
Siamak Hoseinzadeh ◽  
Fardis Nakhaei ◽  
Saim Memon
Keyword(s):  
Carbon Steel ◽  
Modal Analysis ◽  
Natural Frequencies ◽  
Heat Treatments ◽  
Experimental Modal Analysis ◽  
Damping Coefficients

scholarly journals Rayleigh Damping Coefficients of Laminated Rubber Bearing

2019 ◽  
Vol 8 (4) ◽  
pp. 12294-12300
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Natural Frequencies ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Ground Structure ◽  
Damping Coefficients ◽  
Rubber Bearing ◽  
Stability And Instability ◽  
Laminated Rubber Bearing

In isolating the ground structure and the above ground structure from seismic loads, a significant device called laminated rubber bearing is usually found in structure. The complexity of the material which is made up from a combination of rubber and steel shim plates in alternate layer, has made it difficult to measure damping value. Damping is a dissipation of energy or energy losses in the vibration of the structure. Measuring the accurate amount of damping is fundamental as damping plays a crucial role in fixing the borderline between stability and instability in structural systems. Therefore, to determine the damping value including dynamic properties in any materials, modal analysis can be used. Hence, the main objective of this research is to determine the Rayleigh’s damping coefficients α and β and to evaluate the performance of the laminated rubber bearing using finite element and experimental modal analysis. Finding shows that, the finite element modal analysis with the addition of Rayleigh’s damping coefficients α and β, shows a good agreement with the experimental modal analysis in term of natural frequencies and mode shapes. Findings show that, the values of natural frequencies reduced when precise Rayleigh’s damping coefficient added in the finite element modal analysis. It can be concluded that both finite element and experimental modal analysis method can be used to estimate the accurate values of damping ratio and to determine the Rayleigh’s damping coefficients α and β as well.

Experimental Modal Analysis of Fan Vibration Frequency

2011 ◽  
Vol 138-139 ◽  
pp. 395-398
Author(s):  
Li Jun Wang ◽  
Zhi Yang Pan
Keyword(s):  
Modal Analysis ◽  
Vibration Frequency ◽  
Natural Frequencies ◽  
Experimental Modal Analysis ◽  
Resonance Vibration ◽  
Pneumatic Conveying ◽  
Combine Harvester

Fan is used for pneumatic conveying grain in the 4ZTL-1800 combine harvester threshing prior to cutting. In order to decrease power consume of it, the experimental modal analysis of fan was done by using hammer-hitting pulse-inspirit method. The natural frequencies of fan vibration is obtained, which is contrasted with inspirit frequency of fan, then resonance vibration of fan is found and its frequency is at 125Hz, which verifies the result of the experimental modal analysis.The results are beneficial to decrease power consume of fan.

Effect of Weight on the Experimental Modal Analysis of Slender Cantilever Beams

2009 ◽  
Author(s):  
Lawrence Virgin ◽  
David Holland
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Vertical Direction ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Lateral Stiffness ◽  
Axial Loads ◽  
Horizontal Orientation ◽  
Beam System ◽  
Tensile Forces

It is relatively well known that axial loads tend to influence lateral stiffness and hence natural frequencies of slender structural components. Tensile forces tend to increase the lateral stiffness and compressive forces tend to reduce lateral stiffness, bringing with it the possibility of buckling. In many practical situations this is a negligible effect. But for very slender structures it can be important, including the effect of self-weight. This paper will focus attention on a form of double cantilever beam system, i.e., two cantilevers sharing a common hub. A differential axial load can be applied to this system via orientation in a gravitational field. We shall neglect the effect of gravity when the beams are in their horizontal orientation from a limited theoretical standpoint. It is of course present in the experiments but the cantilevers are much stiffer in one direction than the other, and the beams are clamped with their stiffer resistance in the vertical direction. The focus of the current paper is on the natural frequencies and mode shapes of a two-beam system from an experimental modal analysis perspective.

INVESTIGATION OF DYNAMIC PROPERTIES OF ELASTOMERIC BEARING COMPONENTS VIA MODAL ANALYSIS

2015 ◽  
Vol 76 (8) ◽  
Author(s):  
A. I. Yusuf ◽  
M. A. Norliyati ◽  
M. A. Yunus ◽  
M. N. Abdul Rani
Keyword(s):  
Modal Analysis ◽  
Dynamic Behavior ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Seismic Loads ◽  
Ground Structure ◽  
Elastomeric Bearing ◽  
Earthquake Load

Elastomeric bearing is a significant device in structures such as in bridges and buildings. It is used to isolate the ground structure (substructure) and the above ground structure (superstructure) from seismic loads such as earthquake load. Understanding the dynamic behavior of the elastomeric bearing in terms of natural frequencies, mode shapes and damping are increasingly important especially in improving the design and the failure limit of the elastomeric bearing. Modal analysis is one of the methods used to determine the dynamic properties of any materials. Hence, the main objective of this research is to determine the dynamic properties of elastomeric bearing components in terms of natural frequencies, mode shapes, and damping via numerical and experimental modal analysis. This method had been successfully performed in investigating the dynamic behavior of rubber and steel shim plate.

Dynamic Properties of a Heliostat Structure Determined by Numerical and Experimental Modal Analysis

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
J. Felipe Vásquez-Arango ◽  
Reiner Buck ◽  
Robert Pitz-Paal
Keyword(s):  
Modal Analysis ◽  
Vortex Shedding ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Simple Approach ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Fe Model ◽  
Damping Coefficients ◽  
Operating Points

An experimental and numerical modal analysis was performed on an 8 m2 T-shaped heliostat structure at different elevation angles. The experimental results were used to validate a finite element (FE) model by comparing natural frequencies and mode shapes. The agreement between experiments and simulations is good in all operating points investigated. In addition, damping coefficients were determined experimentally for each mode, in order to provide all necessary information for the development of a dynamic model. Furthermore, potentially critical operating conditions caused by vortex shedding were identified using a simple approach.

scholarly journals Computation of Rayleigh damping coefficient of a rectangular submerged floating tunnel (SFT)

2020 ◽  
Vol 2 (5) ◽  
Author(s):  
Md. Hafizur Rahman ◽  
Chhavi Gupta
Keyword(s):  
Dynamic Analysis ◽  
Modal Analysis ◽  
Fundamental Frequency ◽  
Significant Role ◽  
Analytical Study ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Damping Coefficients ◽  
Rayleigh Damping ◽  
Submerged Floating Tunnel

Abstract The dynamic behaviors of the submerged floating tunnel, a buoyant structure of high slenderness, are a matter of concern since it is surrounded by the huge hazardous effects called hydrodynamic, seismic and functional action. Modal analysis and Rayleigh damping coefficients play a significant role in dynamic analysis, but it is not sufficiently simple to predict the reasonable damping coefficients named α and β. The present paper outlines the modal analysis and the calculation of Rayleigh damping coefficients that provide the natural frequencies, mode shapes, mode’s motion as well as coefficients α and β. To compute the Rayleigh damping coefficients, 2–10% damping to the critical damping has been assumed for this analytical study. For the analysis, an FEA-based software ANSYS is utilized successfully. It has been seen that the fundamental frequency and Rayleigh damping coefficients (α = 0.946 and β = 0.00022) of the SFT are reasonably high and it is under noticeable damping.

scholarly journals Natural Frequencies Reduction of RC Slab Subjected to Incremental Concentrated Loads

2019 ◽  
Vol 8 (3) ◽  
pp. 17
Author(s):  
Mezgeen S. Ahmed ◽  
Abdulhameed A. Yaseen ◽  
Fouad A. Mohammad
Keyword(s):  
Reinforced Concrete ◽  
Modal Analysis ◽  
Natural Frequencies ◽  
Concrete Slab ◽  
Experimental Modal Analysis ◽  
Experimental Program ◽  
Concentrated Loads ◽  
Reinforced Concrete Slab ◽  
Reinforced Concrete Slabs ◽  
Set Up

Reinforced concrete slabs are frequently used in many engineering structures such as buildings and bridges. Damages in an engineering structure including reinforced concrete slab are classified as light, moderate, and severe cracks. A special treatment is required for every typical crack-damage to strengthen its structure. The reinforced concrete slab experiencing cracks reduce stiffness as well as its strength. An experimental program was set up to establish a relation between cracks and changes of a dynamic system characteristics of the slab through natural frequencies. The aim is to perform experimental modal analysis (EMA) as a non-destructive vibration testing method for diagnosing the structural integrity of the slab. For this purpose, two RC square slabs specimens of dimensions 1200mm x 1200mm x 40mm were used. As a first part of the project, a reinforced concrete slab was subjected to an increasing partially concentrated loads at the slab’s center to introduce cracks. After each incremental load steps (5, 10, 12kN) the slab was unloaded. Then, a free-free set-up for the slab was established by using the flexible elastic ropes (bungee cords). After the dynamic test of 5, 10 and 12kN loads, the slab was strengthened using external CFRP sheets (type TR30S). Next, experimental modal analysis was performed to establish a relation between cracks and changes in natural frequencies of the slab. The overall trend of frequency decrease after occurring damage that would be expected for all modes. However, it is not guaranteed all modes have same sensitivity to the applied load that inflicts severe cracks.

Modal analysis of violin bodies with back plates made of different wood species

BioResources ◽  
2020 ◽  
Vol 15 (4) ◽  
pp. 7687-7713
Author(s):  
Vasile Ghiorghe Gliga ◽  
Mariana Domnica Stanciu ◽  
Silviu Marian Nastac ◽  
Mihaela Campean
Keyword(s):  
Modal Analysis ◽  
Quality Factor ◽  
Wood Species ◽  
Natural Frequencies ◽  
Musical Instrument ◽  
Experimental Modal Analysis ◽  
Acoustic Properties ◽  
Spectral Components ◽  
The Impact

This research investigated the potential of some European wood species for use in the manufacturing of the back plates of violins as an alternative to the quite rare curly maple wood. An experimental modal analysis was employed for this purpose using the impact hammer method. The modal analysis was performed both on the top and back plates, as individual structures, and then after being integrated into the violin body. The modal analysis envisaged the determination of the eigenfrequencies (natural frequencies), the number of spectral components, and the quality factor, as important indicators of the acoustic performances of a musical instrument. A multi-criteria analysis based on the values obtained for these indicators allowed interesting findings concerning the acoustic properties of the selected wood species (hornbeam, willow, ash, bird-eye maple, walnut, and poplar). Same as curly maple, they all have special aesthetics, but only hornbeam, willow, and ash wood proved to have acoustic potential as well.

Structural Modification of a Pipe Under Harmonic Excitation Using an Hybrid Numerical/Experimental Method

2011 ◽  
Author(s):  
Charles Bodel
Keyword(s):  
Modal Analysis ◽  
Nuclear Power ◽  
Natural Frequencies ◽  
Harmonic Excitation ◽  
Experimental Modal Analysis ◽  
Point Of View ◽  
Mode Shapes ◽  
Design Stage ◽  
Centrifugal Pumps ◽  
Structural Dynamic

Vibrations generated by centrifugal pumps are difficult to predict at the design stage, for it is hardly possible to accurately determine the natural frequencies of pipes and to avoid coincidences with the blade pass frequency of the pump and its harmonics. One is often led to modify the existing structure, by adding stiffness, mass or damping. This paper illustrates this point on a pipe connected to a pump in a nuclear power plant operated by EDF (E´lectricite´ de France). In October 2010, abnormal vibrations were measured on a thin pipe at the outlet of a pump in a powerplant in France. The French nuclear regulatory commission asked EDF to perform a diagnosis and to define solutions within a few months. EDF/R&D division has used an original method developed in 2004 based on hybrid data, and called LMME-SDM (for Local Model Mode-shapes Expansion Structural Dynamic Modification). The main objective is to define a structure modification able to remove all natural frequencies close to the harmonic excitation. For the purpose of the study, we need a numerical model, which should be fairly correct from a static point of view, but which is not necessarily updated from a dynamic point of view, and an experimental modal analysis carried out under real conditions on the pipe. During the experimental modal analysis, a test of added mass has been carried out so that the method can be validated by comparing the predicted and the observed frequency. This method has already been used in industrial cases in former studies [3], however the study presented here has reached a higher level in complexity. Even if this method is able to give reasonable results compared to measurements, it is close to its limits.

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